JSON Schema validator
Validate JSON locally against a Draft 2020-12 schema and inspect instance paths and constraint errors.
Runs on your device · No upload
How to use it
- Paste the Draft 2020-12 schema and the JSON data.
- Validate locally in a browser worker.
- Read the valid/invalid result and the instance locations of any errors.
Validate without changing the data
A JSON Schema describes constraints such as required properties, types, numeric limits and allowed values. The validator reports whether your data satisfies those constraints. It does not coerce strings to numbers, insert defaults or remove unknown properties.
Local references and one explicit dialect
The page evaluates supported Draft 2020-12 keywords through the @cfworker/json-schema interpreter and checks keyword shapes before validating data. Put reusable definitions in $defs and reference them with local fragment references. Remote schemas are not fetched. A schema declaring another draft is rejected rather than evaluated under an undocumented dialect.
Validation is bounded and runs in a worker that can be cancelled. Dynamic references, custom vocabularies and unknown keywords are rejected. Supported format constraints are asserted. Numeric comparisons use JavaScript floating-point arithmetic; uncommon features follow the linked implementation limitations. Schema validity does not prove the factual accuracy or trustworthiness of the data.
Standards and references
Your input stays in this tab
Files and pasted values are processed in your browser. They are not uploaded, stored in your URL or saved to browser storage. Download the result if you want to keep it. CSV exports are limited to 1,000,000 cells and 20 MiB; large or sparse tables must be split. The site records aggregate page requests as described in the privacy policy.